1. Field of the Invention
The present invention relates to a 2-shaft gas turbine including a gas generator and a power turbine.
2. Description of the Related Art
A 2-shaft gas turbine mainly includes a gas generator and a power turbine (a low-pressure turbine) connected to a load, the gas generator employing a compressor, at least one combustor, and a high-pressure turbine. The gas generator and the power turbine each have a rotating shaft and both rotating shafts are not connected to each other. In addition, rotating speeds of the gas generator and the power turbine are controlled independently of each other.
JP-2011-38531-A describes a technology relating to a method for controlling the rotating speed of a rotating shaft on the side of a gas generator. Specifically, JP-2011-38531-A discloses the control method having two control modes in order to solve a sympathetic vibration problem caused by an alteration in rotating speed attributable to a variation in ambient air temperature. In the first control mode, an angle of an inlet guide vane (IGV) of a compressor is adjusted on the basis of the corrected rotating speed of a gas generator shaft which is used when the gas generator rotates at a low speed in accordance with ambient air temperature. In the second control mode, the angle of the inlet guide vane (IGV) of the compressor is adjusted so as to keep constant the actual rotating speed of the gas generator shaft which is used when the gas generator rotates at a high speed.
JP-2011-102548-A describes a technology relating to output control for controlling the output of a gas turbine. Specifically, JP-2011-102548-A discloses a control method in which a target speed is corrected in the following steps. The power output of a low-pressure turbine is first obtained by subtracting a load of a high-pressure turbine from the total output of a turbine. A rotating speed correction value is then computed from the power output thus obtained and an output upper limit value which is set separately. The target speed is lastly corrected on the basis of the rotating speed correction value thus computed.